1. Field of the Invention
The present invention relates to a high efficiency welding process and apparatus wherein a welding electrode and arc are both oscillated.
2. Description of the Prior Art
Heretofore, in order to improve the efficiency of metal arc welding, the amount of the deposited metal formed by one welding pass has been increased by increasing the welding current. Since the welding current cannot be greatly increased in the horizontal or the vertical welding position, oscillation of the welding electrode has been adopted to perform horizontal or vertical welding as the easiest and the most practical method to increase the amount of deposited metal. For example U.S. Pat. No. 3,832,522 discloses a vertical upward welding process and apparatus wherein the welding electrode is oscillated across the welding line.
As a result of the increasing demand for the welding of thick metal plates, a narrow gap groove joint has recently been substituted for the X--groove joint in view of the necessary amount of the deposited metal. However, with mere oscillation of the welding electrode, the groove faces at the both sides of the narrow gap groove are not penetrated enough, because the welding arc is weak in the direction of the groove face. Thus the defects such as lack of fusion may occur and a sound weld cannot consistently be obtained. Especially in the case of thick plates of aluminum or aluminum alloy sufficient penetration to the groove face cannot be obtained.
U.S. Pat No. 3,328,556 discloses a welding process wherein the welding arc is generated between a non-consumable electrode and the thick plates to be welded, filler wire is fed to the narrow gap, and the non-consumable electrode is oscillated across the welding line.
It is known to direct a welding arc towards a predetermined position within the welding groove. For example, German lay open print DT-OS 2,325,708 (corresponding to U.S. Pat. No. 3,941,974) discloses an arc welding process wherein a welding electrode is placed within the welding groove in a flat welding position so that the electrode is electrically insulated from the plates to be welded, and the arc between the electrode and the plates to be welded is directed towards the predetermined position of the welding groove by a magnetic force.
However, these conventional processes do not teach how to perform high efficiency welding of a narrow gap horizontal or vertical welding groove formed between thick metal plates how to be welded and to obtain sufficient penetration to the groove faces of the narrow groove. Accordingly, there is a need for a high efficiency welding process and apparatus to produce the above mentioned results.